linux-kernel - Re: Allocating buffers for USB transfers (again)

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Date:	Fri, 12 Aug 2011 01:29:53 +0200
From:	Matěj Laitl <matej@...tl.cz>
To:	Daniel Mack <zonque@...il.com>
Cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Florian Mickler <florian@...kler.org>,
	Oliver Neukum <oliver@...kum.org>, linux-usb@...r.kernel.org,
	alsa-devel@...a-project.org, Takashi Iwai <tiwai@...e.de>,
	Clemens Ladisch <clemens@...isch.de>, pedrib@...il.com,
	William Light <wrl@...est.net>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org, Robert Hancock <hancockrwd@...il.com>
Subject: Re: Allocating buffers for USB transfers (again)

On 11. 8. 2011 Daniel Mack wrote:
> On Thu, Aug 11, 2011 at 8:05 PM, Sarah Sharp
> > Because according to Matej, he applied that patch, plus my patch to
> > reject zero-length buffers[1], and he saw debugging that indicated he
> > *did* see zero-length buffers.  Is there any chance your driver might
> > submit a zero-length buffer in the middle of the isochronous URB
> > transfer array?
> 
> Hmm, judging from the code, this can only ever happen if we receive an
> inbound iso frame which has a valid status and an actual_length of
> zero. Also, it was not neccessary to catch this case for EHCI.
> 
> Maetj, does this patch make any difference?

This patch actually makes the sound playback _worse_. Now I get strange 
squawks where previously at least first seconds of a song sounded normally.

However, I no longer get "zero length buffer submitted" or that "... Weird." 
debug messages, only several megabytes of: (should I post these somewhere?)

xhci_hcd 0000:05:00.0: Giveback URB ffff880114cec000, len = 880, expected = 
1000, status = -115
xhci_hcd 0000:05:00.0: Giveback URB ffff880114740000, len = 352, expected = 
1000, status = -115
xhci_hcd 0000:05:00.0: underrun event on endpoint

Regards,
                 Matej
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